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Post by matt@IAA on Apr 20, 2018 13:05:37 GMT -6
Got all the op amp kinks sorted out. Running my CAPI ACA-BO rig right now with homemade op amps and power supply.
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Post by matt@IAA on Apr 25, 2018 14:55:51 GMT -6
So... the prototype I'm making is really and truly designed as the front end for a DAW. As of right now, I didn't put in a post-BTA level pot, because I figure you'd be doing automation and setting levels in the DAW, plus probably sending some kind of subgrouping in the digital domain. I'm using passive panning, so there's a very slight boost across the balanced amplifiers in order to have the post-pan bus at a nominal -2 dB with a +4 input. It does have an insert point, -2 unbalanced just before the master fader. Does anyone actually use true insert cables any more? Or would people prefer a pair of jacks (in, out)? Anyone know a reasonable alternative to mill-max PCB socket pins? They're 10% of the component cost in this thing.
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Post by wiz on Apr 25, 2018 19:29:05 GMT -6
So... the prototype I'm making is really and truly designed as the front end for a DAW. As of right now, I didn't put in a post-BTA level pot, because I figure you'd be doing automation and setting levels in the DAW, plus probably sending some kind of subgrouping in the digital domain. I'm using passive panning, so there's a very slight boost across the balanced amplifiers in order to have the post-pan bus at a nominal -2 dB with a +4 input. It does have an insert point, -2 unbalanced just before the master fader. Does anyone actually use true insert cables any more? Or would people prefer a pair of jacks (in, out)? Anyone know a reasonable alternative to mill-max PCB socket pins? They're 10% of the component cost in this thing. In and Out cool stuff bud Cheers Wiz
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Post by matt@IAA on May 2, 2018 13:13:43 GMT -6
Tested one channel real quick, the balanced differential amps work. Gonna build out the test case next.
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Post by matt@IAA on May 2, 2018 19:15:06 GMT -6
Assuming this all works out here in the next week or two - anyone want to demo this?
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Post by matt@IAA on May 2, 2018 20:27:53 GMT -6
Also — most important of all maybe — what kind of knobs?!
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Post by wiz on May 2, 2018 20:39:29 GMT -6
If I were close I would love to
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ericn
Temp
Balance Engineer
Posts: 14,934
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Post by ericn on May 10, 2018 7:32:05 GMT -6
So... the prototype I'm making is really and truly designed as the front end for a DAW. As of right now, I didn't put in a post-BTA level pot, because I figure you'd be doing automation and setting levels in the DAW, plus probably sending some kind of subgrouping in the digital domain. I'm using passive panning, so there's a very slight boost across the balanced amplifiers in order to have the post-pan bus at a nominal -2 dB with a +4 input. It does have an insert point, -2 unbalanced just before the master fader. Does anyone actually use true insert cables any more? Or would people prefer a pair of jacks (in, out)? Anyone know a reasonable alternative to mill-max PCB socket pins? They're 10% of the component cost in this thing. There are cheaper ones if you buy in huge quantities, but they are crap, inconsistent size and very fragile, so Mill-Max is the way to go.
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Post by Blackdawg on May 10, 2018 14:22:57 GMT -6
Stoked to see the result! And hear it.
I like aluminum knobs personally..but they aren't cheap.
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Post by matt@IAA on May 10, 2018 16:13:46 GMT -6
I ran out of molex crimp terminals, and I'm waiting on the transformers to come in. I guess I'll make more op amps while I wait. Suspense is killing me. Or work on this...
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Post by Blackdawg on May 10, 2018 16:59:05 GMT -6
I ran out of molex crimp terminals, and I'm waiting on the transformers to come in. I guess I'll make more op amps while I wait. Suspense is killing me. Or work on this... What program is that you use to design the PCBs? Also why Molex crimps? I like using the Phonix or whatever terminals way more. Makes wiring much easier.
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Post by matt@IAA on May 10, 2018 17:15:36 GMT -6
AutoCAD Eagle or EasyEDA.
I don't know, it's just what I've seen and used. Got a mouser link to what you're talking about?
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Post by Blackdawg on May 10, 2018 18:07:20 GMT -6
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Post by matt@IAA on May 12, 2018 19:07:26 GMT -6
All wired up and working without transformers. Gain staging works out like the math says. Now I just need my transformers.
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Post by Blackdawg on May 12, 2018 19:52:35 GMT -6
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Post by matt@IAA on May 12, 2018 21:34:38 GMT -6
That’s price looks better than the others haha.
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Post by matt@IAA on May 28, 2018 22:27:19 GMT -6
Finally got my transformers. Assuming I get a free moment this week I’ll have some samples here shortly.
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Post by matt@IAA on Jun 2, 2018 13:47:30 GMT -6
OK. Finally had a chance to get everything installed. No samples yet, but I got some testing done.
Test setup is on the 8 into 2 box, so both L and R channels are always summing 8 inputs (no cheating by channel switching off!)
Frequency Response - 44 kOhm load +0.08 / -0.64 dB from 20 Hz to 15 kHz (limit of my testing software - the high end rolloff is caused by the LPF on the interface I'm using which has a -3 dB point at 22 kHz)
Noise RMS power (A-weighted):-90.4 dB at bus outputs
THD and Noise - THD - 0.009% THD+N - 0.014% THD+N (A-weighted) - 0.015% IMD+Noise (A-weighted) - 0.017% IMD @ 10kHz - 0.019%
Stereo crosstalk (bus to bus) -68.5 dB
All of the IMD is coming from 60 Hz and harmonics, I may be able to get it down. Maybe it doesn't matter.
Also, my interface looped back on itself is -94 dB on noise so I’m not sure those numbers wouldn’t be improved by more robust testing. At any rate, it’s a quieter than some of my other gear.
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Post by matt@IAA on Jun 2, 2018 18:21:04 GMT -6
Edit: Ill get some better samples posted.
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Post by matt@IAA on Jun 4, 2018 10:54:12 GMT -6
A is a with the box, b without. Level matched as best I could
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Post by Blackdawg on Jun 4, 2018 14:54:34 GMT -6
Interesting results. The box adds some low end punch and tightness to it most the time. Stereo image is a bit wider in the later examples too. Im sure its more obvious with not an mp3 and if you could live A/B the two.
Great job!
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Post by wiz on Jun 4, 2018 17:17:27 GMT -6
B
cheers
Wiz
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Post by matt@IAA on Jun 5, 2018 2:17:34 GMT -6
Edit to put new samples.
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Post by matt@IAA on Jun 12, 2018 12:46:13 GMT -6
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Post by mythundreamt on Jun 14, 2018 12:43:17 GMT -6
Wow that sounds great! The drums have a subtle (but not imaginary) punchiness and 3D depth added, but the guitars really came alive with noticeable op-amp punch! I listened blind without reading the title and picked the ana version every time, although it was harder with the drums.
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